In recent years, the number and diversity of electronic parts to be installed in automobiles has increased rapidly. As a result, the circuits contained in automotive electrical connection boxes have also been increased. In an attempt to form high density branch circuits, busbars and pressure-connections between the wire and the terminal have been used. As shown particularly in FIG. 3, busbars 7 and 8 are to be connected to each other. However, busbar 9 is located between them. In order to avoid electrical contact between busbars 7 and 8 and busbar 9, wire 6 is pressed between blades 11, thereby avoiding busbar 9 and securing the electrical connection between busbars 7 and 8.
As shown in FIG. 4, insulative plate 4D carries busbars 7 and 8. Connection sections 10 pass through openings 17 in insulative plate 4E and blades 11 cut through the insulation on wires 6 to make electrical contact with the cores thereof. A further modification is shown in FIG. 5, wherein insulative plate 4C carries busbar 9 and insulative plate 4D carries busbars 7 and 8. Connection section 10 of busbar 9 passes through opening 17 in insulative plate 4D and through opening 17 in insulative plate 4E. Since busbars 7 and 8 are resting on insulative plate 4D, connection sections 10 thereof only have to pass through openings 17 in insulation plate 4E. However, since busbar 9 rests on insulative plate 4C, section 10 passes through openings 17 in plates 4D and 4E.
However, the busbar method is such that an increased number of circuits in the connection box is accompanied by a decrease in the number of circuits which can be placed on a single layer. Thus, a greater number of layers must be provided, thereby making the connection box larger and more complex.
On the other hand, if pressure-connection methods are used, the circuit density is increased and design changes can be readily implemented; however, greater equipment costs result. In some cases, the two methods are combined. In such structures, busbar layers are stacked with layers formed from wires and pressure-connection terminals. These layers are connected to external circuits. However, this combined method results in higher production costs, creating problems in manufacture of low cost automobiles.